For the past 100 years, The City has fought for the Palace of Fine Arts. That struggle continues today.

Originally built as a temporary structure for the 1915 Panama-Pacific International Exposition, it was only supposed to exist for one year. But the structure was so beloved that a group of citizens fought to preserve the palace, turning it into The City’s first art museum.

Over the decades, San Francisco residents reaffirmed their support, approving a $1.8 million bond in 1959 to recast the palace in permanent materials. The City also undertook a seismic retrofit in 1993, and a $21 million renovation of the grounds and rotunda in 2010.

It is both encouraging and troubling that this week thousands of citizens again rose up again to demand its preservation as an educational and cultural space: Encouraging because the public evidently still believes the Palace is a public asset worth fighting for, troubling because citizens have to fight against yet another threat to the site, this time what they see as The City’s attempt to auction off the Palace for financial gain.

The Recreation and Park Commission is seeking a new tenant to take over the long-term lease on the structure that formerly housed the Exploratorium. The three finalists, approved by the Operations Committee last week, include two hotels and at least one restaurant. The finalists also include some combination of historic displays, galleries or event facilities.

San Francisco resident Kirsten Selberg created an online petition on Saturday urging Rec and Park and Mayor Ed Lee not to sell out the site and preserve it as a cultural and educational center. The petition had garnered more than 15,000 signatures as of Wednesday afternoon.

“These things are important to San Franciscans, especially with what we’re dealing with right now, such rapid change in The City that’s not necessarily for the best,” Selberg said. “San Franciscans are just begging to hang on to something for themselves and for The City.”

Rec and Park is looking for the next tenant to take on a lease for up to 55 years and repair the 143,996-square-foot palace. The full commission is slated to weigh in on the recommendations on Nov. 19, and a winner could be selected as early as next summer.

Sarah Ballard, a spokeswoman for Rec and Park, told the San Francisco Examiner the goal is to find a tenant that “increases public access, that allows for the $20 million necessary to bring the building up to code, and that continues to enhance the cultural fabric of San Francisco.”

The City must find a tenant who will be a good steward of the building and the site, but in a time of such heralded prosperity for The City, hawking such a public treasure on the basis of who can bring the highest return seems an unfortunate policy for The City to adopt. The City can surely afford to safeguard such a significant part of our heritage if the political will is there.

We applaud the petition supporters for standing up for their city, for reminding our officials that San Francisco is still a city they feel they have a stake in and want a say in its future.

If the Palace of Fine Arts becomes a hotel for tourists or a restaurant for the wealthy, it would be more than a missed opportunity for San Francisco. It would be seen by some, and rightly so, as a repudiation of our civic responsibility to hold our public treasure in trust.

It may very well be that one of these recommended proposals contain the right combination of financial stability, artistic programming and educational foundation that makes sense for the next tenant of the Palace, and we hope that’s the case. But it is heartening to see 15,000 people speak up to ensure our leaders are doing all they can to preserve a jewel we can’t afford to tarnish.